The integration of TFRs in semiconductor devices enables resistance to relatively large current density. As illustrated in FIG. 3, a conventional polysilicon resistor 301 is formed over STI 303. Contacts 305 are formed directly on the resistor. In order to attain high resistance, the TFRs normally are formed to a very thin thickness of between 30 Angstrom (Å) to 300 Å. Furthermore, in some high precision applications, there is a need for resistors with very closely matched resistance. Hence it is important that the resistance of integrated TFRs is controllable and predictable during the fabrication process. However, vias (for forming the contacts) formed directly over the TFRs can easily penetrate through the thin TFRs, causing undesirable variance in the end contact resistance. This leads to a mismatch of the TFRs and results in deteriorated TFR reliability and overall circuit performance.
In a conventional process, material 117 typically has low temperature coefficient. Examples of material 117 include tantalum (Ta), tantalum nitride (TaN), silicon chromium (SiCr), or nickel chromium (NiCr). Etching of material 117 typically requires special etching chemistry and equipment, hence special equipment such as a RIE etcher may be needed, or tool dedication specific for the etch process may be practiced. This could pose a significant increase in the manufacturing cost.
A need therefore exists for methodology enabling manufacture of a TFR without via penetration and the resulting device.